get off your backside

[tree123]

Cambridge Dictionary defines 'get off your backside' as 'stop being lazy'.

The phrase reminds me of an image of a person is sitting idlely, and s/he gets up to work. Am I correct? If no, would someone please explain why that means 'stop being lazy'?

 

[tedmc]

In AmE, it is get off your ass.

Isn't that a bit crude to be used by a politician (said by a British politician in tree123's other post)?

 

[PeterCW]

The dictionary is giving the polite version. A cruder term for that part of the body would often be used in real life.

 

[Skrej]

In AmE, it is get off your ass.

While you might hear that in AmE, don't assume it's the only version. You're just as likely to hear 'butt', 'rear' or 'backside' as 'ass'.